[Xamarin.Android.Build.Tasks] Use ProGuard config files from .aar files. (#5310)

Fixes: #3752

`.aar` [can contain `proguard.txt` files][0]

> **Library dependencies**
> *Location*: AAR libraries: `<library-dir>/proguard.txt`
> *Description*: If an AAR library is published with its own ProGuard
> rules file, and you include that AAR as a compile-time dependency,
> R8 automatically applies its rules when compiling your project.

Update the `@(ProguardConfiguration)` item group to include
`proguard.cfg` and `proguard.txt` files in the project directory, and
for Library project builds add the contents of all
`@(ProguardConfiguration)` files into a `proguard.txt` entry within
the generated `.aar` file (fcd7cf8).

Update the `_ResolveLibraryProjectImports` target and the
`<ResolveLibraryProjectImports/>` MSBuild task to look for
`proguard.txt` files contained within `.aar` packages, and update the
`<ReadLibraryProjectImportsCache/>` MSBuild task so that
`proguard.txt` files within `.aar` packages are added to the
`@(ProguardConfiguration)` item group of App builds, so that they are
appropriately passed to the `_CompileToDalvik` target and used when
converting Java bytecode into Dalvik bytecode.

TODO?

The Android documentation mentions that `.jar` files can also contain
ProGuard files:

> *Location*: JAR libraries: `<library-dir>/META-INF/proguard/`

We do not currently use ProGuard files contained within `.jar` files.

[0]: https://developer.android.com/studio/build/shrink-code

Author: dellis1972

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/Sdk/AutoImport.props

@@ -45,6 +45,8 @@ https://github.com/dotnet/designs/blob/4703666296f5e59964961464c25807c727282cae/
     <AndroidNativeLibrary Include="**\*.so"  Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder)" />
     <JavaSourceJar        Include="**\*-source.jar;**\*-sources.jar;**\*-src.jar"   Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder)" />
     <AndroidJavaSource    Include="**\*.java" Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder)" />
+    <ProguardConfiguration Include="**\proguard.cfg" Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder)" />
+    <ProguardConfiguration Include="**\proguard.txt" Exclude="$(DefaultItemExcludes);$(DefaultExcludesInProjectFolder)" />
   </ItemGroup>
 
 </Project>

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.AndroidLibraries.targets

@@ -49,6 +49,7 @@ projects.
       <_CreateAarInputs Include="@(AndroidJavaLibrary)" />
       <_CreateAarInputs Include="@(EmbeddedJar)" />
       <_CreateAarInputs Include="@(EmbeddedNativeLibrary)" />
+      <_CreateAarInputs Include="@(ProguardConfiguration)" />
     </ItemGroup>
     <Hash
         ItemsToHash="@(_CreateAarInputs)"
@@ -80,6 +81,7 @@ projects.
         AndroidEnvironment="@(AndroidEnvironment)"
         JarFiles="@(AndroidJavaLibrary);@(EmbeddedJar)"
         NativeLibraries="@(EmbeddedNativeLibrary)"
+        ProguardConfigurationFiles="@(ProguardConfiguration)"
         OutputFile="$(_AarOutputPath)"
     />
     <ItemGroup>

src/Xamarin.Android.Build.Tasks/Tasks/CreateAar.cs

@@ -23,6 +23,8 @@ public class CreateAar : AndroidTask
 
 		public ITaskItem [] NativeLibraries { get; set; }
 
+		public ITaskItem [] ProguardConfigurationFiles { get; set; }
+
 		[Required]
 		public string AssetDirectory { get; set; }
 
@@ -103,6 +105,13 @@ public override bool RunTask ()
 						existingEntries.Remove (archivePath);
 					}
 				}
+				if (ProguardConfigurationFiles != null) {
+					var sb = new StringBuilder ();
+					foreach (var file in ProguardConfigurationFiles) {
+						sb.AppendLine (File.ReadAllText (file.ItemSpec));
+					}
+					aar.AddEntry ("proguard.txt", sb.ToString (), Files.UTF8withoutBOM);
+				}
 				foreach (var entry in existingEntries) {
 					Log.LogDebugMessage ($"Removing {entry} as it is not longer required.");
 					aar.DeleteEntry (entry);

src/Xamarin.Android.Build.Tasks/Tasks/ReadLibraryProjectImportsCache.cs

@@ -1,21 +1,21 @@
-// 
+//
 // ReadLibraryProjectImportsCache.cs
-//  
+//
 // Author:
 //       Dean Ellis <[email protected]>
-// 
+//
 // Copyright (c) 2015 Xamarin Inc.
-// 
+//
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
 // in the Software without restriction, including without limitation the rights
 // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 // copies of the Software, and to permit persons to whom the Software is
 // furnished to do so, subject to the following conditions:
-// 
+//
 // The above copyright notice and this permission notice shall be included in
 // all copies or substantial portions of the Software.
-// 
+//
 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
@@ -38,7 +38,7 @@ public class ReadLibraryProjectImportsCache : AndroidTask
 		public override string TaskPrefix => "RLC";
 
 		[Required]
-		public string CacheFile { get; set;} 
+		public string CacheFile { get; set;}
 
 		[Output]
 		public ITaskItem [] Jars { get; set; }
@@ -55,6 +55,9 @@ public class ReadLibraryProjectImportsCache : AndroidTask
 		[Output]
 		public ITaskItem [] ResolvedResourceDirectoryStamps { get; set; }
 
+		[Output]
+		public ITaskItem [] ProguardConfigFiles { get; set; }
+
 		public override bool RunTask ()
 		{
 			Log.LogDebugMessage ("Task ReadLibraryProjectImportsCache");
@@ -70,12 +73,14 @@ public override bool RunTask ()
 			ResolvedEnvironmentFiles = doc.GetPathsAsTaskItems ("ResolvedEnvironmentFiles", "ResolvedEnvironmentFile");
 			ResolvedResourceDirectoryStamps = doc.GetPathsAsTaskItems ("ResolvedResourceDirectoryStamps"
 				, "ResolvedResourceDirectoryStamp");
-			
+			ProguardConfigFiles = doc.GetPathsAsTaskItems ("ProguardConfigFiles", "ProguardConfigFile");
+
 			Log.LogDebugTaskItems ("  Jars: ", Jars);
 			Log.LogDebugTaskItems ("  ResolvedAssetDirectories: ", ResolvedAssetDirectories);
 			Log.LogDebugTaskItems ("  ResolvedResourceDirectories: ", ResolvedResourceDirectories);
 			Log.LogDebugTaskItems ("  ResolvedEnvironmentFiles: ", ResolvedEnvironmentFiles);
 			Log.LogDebugTaskItems ("  ResolvedResourceDirectoryStamps: ", ResolvedResourceDirectoryStamps);
+			Log.LogDebugTaskItems ("  ProguardConfigFiles: ", ProguardConfigFiles);
 
 			return !Log.HasLoggedErrors;
 		}

src/Xamarin.Android.Build.Tasks/Tasks/ResolveLibraryProjectImports.cs

@@ -59,6 +59,9 @@ public class ResolveLibraryProjectImports : AndroidTask
 		[Output]
 		public ITaskItem [] ResolvedResourceDirectoryStamps { get; set; }
 
+		[Output]
+		public ITaskItem [] ProguardConfigFiles { get; set; }
+
 		internal const string OriginalFile = "OriginalFile";
 		internal const string AndroidSkipResourceProcessing = "AndroidSkipResourceProcessing";
 
@@ -83,10 +86,11 @@ public override bool RunTask ()
 			var resolvedResourceDirectories   = new List<ITaskItem> ();
 			var resolvedAssetDirectories      = new List<ITaskItem> ();
 			var resolvedEnvironmentFiles      = new List<ITaskItem> ();
+			var proguardConfigFiles           = new List<ITaskItem> ();
 
 			assemblyMap.Load (AssemblyIdentityMapFile);
 			try {
-				Extract (jars, resolvedResourceDirectories, resolvedAssetDirectories, resolvedEnvironmentFiles);
+				Extract (jars, resolvedResourceDirectories, resolvedAssetDirectories, resolvedEnvironmentFiles, proguardConfigFiles);
 			} catch (ZipIOException ex) {
 				Log.LogCodedError ("XA1004", ex.Message);
 				Log.LogDebugMessage (ex.ToString ());
@@ -96,6 +100,7 @@ public override bool RunTask ()
 			ResolvedResourceDirectories = resolvedResourceDirectories.ToArray ();
 			ResolvedAssetDirectories    = resolvedAssetDirectories.ToArray ();
 			ResolvedEnvironmentFiles    = resolvedEnvironmentFiles.ToArray ();
+			ProguardConfigFiles         = proguardConfigFiles.ToArray ();
 
 			ResolvedResourceDirectoryStamps = ResolvedResourceDirectories
 				.Select (s => new TaskItem (Path.GetFullPath (Path.Combine (s.ItemSpec, "../..")) + ".stamp"))
@@ -116,14 +121,15 @@ public override bool RunTask ()
 						new XElement ("Jars",
 							Jars.Select(e => new XElement ("Jar", e))),
 						new XElement ("ResolvedResourceDirectories",
-							ResolvedResourceDirectories.ToXElements ("ResolvedResourceDirectory", knownMetadata)
-							),
+							ResolvedResourceDirectories.ToXElements ("ResolvedResourceDirectory", knownMetadata)),
 						new XElement ("ResolvedAssetDirectories",
 							ResolvedAssetDirectories.ToXElements ("ResolvedAssetDirectory", knownMetadata)),
 						new XElement ("ResolvedEnvironmentFiles",
 							ResolvedEnvironmentFiles.ToXElements ("ResolvedEnvironmentFile", knownMetadata)),
 						new XElement ("ResolvedResourceDirectoryStamps",
-							ResolvedResourceDirectoryStamps.ToXElements ("ResolvedResourceDirectoryStamp", knownMetadata))
+							ResolvedResourceDirectoryStamps.ToXElements ("ResolvedResourceDirectoryStamp", knownMetadata)),
+						new XElement ("ProguardConfigFiles",
+							ProguardConfigFiles.ToXElements ("ProguardConfigFile", knownMetadata))
 					));
 				document.SaveIfChanged (CacheFile);
 			}
@@ -135,6 +141,7 @@ public override bool RunTask ()
 			Log.LogDebugTaskItems ("  ResolvedAssetDirectories: ", ResolvedAssetDirectories);
 			Log.LogDebugTaskItems ("  ResolvedEnvironmentFiles: ", ResolvedEnvironmentFiles);
 			Log.LogDebugTaskItems ("  ResolvedResourceDirectoryStamps: ", ResolvedResourceDirectoryStamps);
+			Log.LogDebugTaskItems ("  ProguardConfigFiles:", ProguardConfigFiles);
 
 			return !Log.HasLoggedErrors;
 		}
@@ -145,7 +152,8 @@ void Extract (
 				IDictionary<string, ITaskItem> jars,
 				ICollection<ITaskItem> resolvedResourceDirectories,
 				ICollection<ITaskItem> resolvedAssetDirectories,
-				ICollection<ITaskItem> resolvedEnvironments)
+				ICollection<ITaskItem> resolvedEnvironments,
+				ICollection<ITaskItem> proguardConfigFiles)
 		{
 			// lets "upgrade" the old directory.
 			string oldPath = Path.GetFullPath (Path.Combine (OutputImportDirectory, "..", "__library_projects__"));
@@ -345,6 +353,7 @@ void Extract (
 				string resDir = Path.Combine (importsDir, "res");
 				string resDirArchive = Path.Combine (resDir, "..", "res.zip");
 				string assetsDir = Path.Combine (importsDir, "assets");
+				string proguardFile = Path.Combine (importsDir, "proguard.txt");
 
 				bool updated = false;
 				string aarHash = Files.HashFile (aarFile.ItemSpec);
@@ -431,6 +440,11 @@ void Extract (
 					resolvedAssetDirectories.Add (new TaskItem (Path.GetFullPath (assetsDir), new Dictionary<string, string> {
 						{ OriginalFile, aarFullPath },
 					}));
+				if (File.Exists (proguardFile)) {
+					proguardConfigFiles.Add (new TaskItem (Path.GetFullPath (proguardFile), new Dictionary<string, string> {
+						{ OriginalFile, aarFullPath },
+					}));
+				}
 			}
 		}
 

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/XASdkTests.cs

@@ -62,6 +62,9 @@ public void DotNetBuildLibrary (bool isRelease, bool duplicateAar)
 					new AndroidItem.AndroidResource (() => "Resources\\drawable\\IMALLCAPS.png") {
 						BinaryContent = () => XamarinAndroidApplicationProject.icon_binary_mdpi,
 					},
+					new AndroidItem.ProguardConfiguration ("proguard.txt") {
+						TextContent = () => @"-ignorewarnings",
+					},
 				}
 			};
 			libC.OtherBuildItems.Add (new AndroidItem.AndroidAsset ("Assets\\bar\\bar.txt") {
@@ -73,6 +76,13 @@ public void DotNetBuildLibrary (bool isRelease, bool duplicateAar)
 			var libCBuilder = CreateDotNetBuilder (libC, Path.Combine (path, libC.ProjectName));
 			Assert.IsTrue (libCBuilder.Build (), $"{libC.ProjectName} should succeed");
 
+			var aarPath = Path.Combine (FullProjectDirectory, libC.OutputPath, $"{libC.ProjectName}.aar");
+			FileAssert.Exists (aarPath);
+			using (var aar = ZipHelper.OpenZip (aarPath)) {
+				aar.AssertContainsEntry (aarPath, "assets/bar/bar.txt");
+				aar.AssertContainsEntry (aarPath, "proguard.txt");
+			}
+
 			var libB = new XASdkProject (outputType: "Library") {
 				ProjectName = "LibraryB",
 				IsRelease = isRelease,
@@ -111,6 +121,9 @@ public Foo ()
 						Encoding = Encoding.ASCII,
 						TextContent = () => ResourceData.JavaSourceTestExtension,
 					},
+					new AndroidItem.ProguardConfiguration ("proguard.txt") {
+						TextContent = () => @"-ignorewarnings",
+					},
 				}
 			};
 			libB.OtherBuildItems.Add (new AndroidItem.AndroidEnvironment ("env.txt") {
@@ -140,7 +153,7 @@ public Foo ()
 
 			// Check .aar file for class library
 			var libBOutputPath = Path.Combine (FullProjectDirectory, libB.OutputPath);
-			var aarPath = Path.Combine (libBOutputPath, $"{libB.ProjectName}.aar");
+			aarPath = Path.Combine (libBOutputPath, $"{libB.ProjectName}.aar");
 			FileAssert.Exists (aarPath);
 			FileAssert.Exists (Path.Combine (libBOutputPath, "bar.aar"));
 			using (var aar = ZipHelper.OpenZip (aarPath)) {
@@ -196,6 +209,8 @@ public Foo ()
 			var intermediate = Path.Combine (FullProjectDirectory, appA.IntermediateOutputPath);
 			var dexFile = Path.Combine (intermediate, "android", "bin", "classes.dex");
 			FileAssert.Exists (dexFile);
+			var proguardFiles = Directory.GetFiles (Path.Combine (intermediate, "lp"), "proguard.txt", SearchOption.AllDirectories);
+			Assert.AreEqual (2, proguardFiles.Length, "There should be only two proguard.txt files.");
 			string className = "Lcom/xamarin/android/test/msbuildtest/JavaSourceJarTest;";
 			Assert.IsTrue (DexUtils.ContainsClass (className, dexFile, AndroidSdkPath), $"`{dexFile}` should include `{className}`!");
 			className = "Lcom/xamarin/android/test/msbuildtest/JavaSourceTestExtension;";

src/Xamarin.Android.Build.Tasks/Xamarin.Android.EmbeddedResource.targets

@@ -55,6 +55,7 @@ This file is used by all project types, including binding projects.
       <Output TaskParameter="ResolvedAssetDirectories" ItemName="LibraryAssetDirectories" />
       <Output TaskParameter="ResolvedEnvironmentFiles" ItemName="LibraryEnvironments" />
       <Output TaskParameter="ResolvedResourceDirectoryStamps" ItemName="_LibraryResourceDirectoryStamps" />
+      <Output TaskParameter="ProguardConfigFiles" ItemName="ProguardConfiguration" />
     </ReadLibraryProjectImportsCache>
     <ItemGroup>
       <FileWrites Include="@(ResolvedResourceDirectories->'%(ResourceDirectoryArchive)')"